The invention relates to an arrangement for operating valves of an internal combustion engine by means of several cams and several rocker arms which are disposed adjacent to one another and can be joined or disconnected by a control pin axially movable through guide bores formed in the rocker arms.
EP 02 65 281 B1 discloses an arrangement for operating inlet and outlet valves of an internal combustion engine with several rocker arms for the opening and closing of the valves and cams for operating the rocker arms which include guide bores to be arranged in alignment with one another. The guide bores have axially movable connecting pins extending across two adjacent rocker arms for their interconnection and are axially movable in the guide bores for selectively disconnecting or joining two adjacent rocker arms.
For general background further reference is made to patent publications DE 42 21 134 C1 and EP 02 93 209 B1.
It is a disadvantage of these arrangements that, because of the short shifting times for the pins, it is necessary to provide relatively large clearances between the support surfaces of the control pins and the guide bores in order to insure movement of the control pins while the guide bores are in alignment with one another. However, the relatively large clearance is problematic insofar as the control pins become cogged when they are disposed between two rocker arms for their interconnection such that the surface area of the pin providing for engagement is relatively small and the high surface pressure caused thereby results in relatively high wear of the engagement areas between the control pin and the guide bores. Furthermore, the relatively large clearance of the control pins in the guide bores causes annoying operating noises of the valve operating mechanism.
A further disadvantage of such an arrangement resides in the fact that, because of the relatively large clearance, the valve overlap has to be relatively large which causes a relatively large amount of combustion gases to remain in the cylinder at the end of the exhaust stroke of the engine.
It is the object of the present invention to provide a valve operating mechanism which, while still providing for reliable operation of the control pin in the aligned position of the guide bores, will permit a reduction of the valve over-lap and will provide therefore for a reduction of the amount of exhaust gases remaining in the cylinder at the end of the exhaust stroke of the engine.